Ovens for cooking and heating foods are well known in the art. Some of these ovens facilitate convective cooking in which heat is indirectly transferred to the food through the air between the heat source and that food. Other ovens facilitate conductive cooking where the food is heated by direct contact with a surface at an elevated temperature.
A few ovens provide combinations of convective and conductive cooking. U.S. Pat. No. 4,224,862 discloses a shelf and serpentine, widely spaced-apart hollow tubing within that shelf for the transport of heating fluids.
Trays or shelves for a hot food cabinet are disclosed in FIGS. 4 and 5 of U.S. Pat. No. 3,030,486. This patent further discloses electric heating elements and steam as a heating medium.
A prior experimental apparatus developed by the inventor of the present invention features a vertical cabinet having a plurality of individually thermalized, vertically spaced-apart rectangular support shelves. These shelves are made from a heat conductive material. Specifically, the shelves are made from two aluminum sheets of differing thickness. The thicker sheet, having a thickness of about 40/1000th inch, defines a top surface of the shelf. The thinner sheet, having a thickness of about 30/1000th inch, defines a bottom surface. The two shelves are roll-bonded together in a manner that forms by expansion a serpentine fluid channel in the bottom surface. A heated fluid may be passed through the channel by a fluid inlet and outlet positioned along one width side of the shelf. As a result of such inlet positioning, the serpentine channel undulates in a manner parallel to the shelf width.
While the foregoing prior art device was an improvement over prior art heating and holding cabinets, it was determined that the top surface sheet was insufficiently thick. This caused the top surface to become uneven and indented during the roll-bonding process. As a result, the top surface had high and low spots which prevented even and uniform conductive thermalization of a food product placed thereon. In addition, the undulation of the serpentine channel in a manner generally parallel to the width of the shelf did not efficiently and uniformly thermalize the complete surface area of the top surface of the shelf. Unthermalized zones on the top surface thereby resulted.
In addition, refrigeration technology is known in the art. A prior art device that provides for both heating and refrigeration features is disclosed in U.S. Pat. No. 4,235,282 to de Filippis et al. This patent discloses a tray cabinet comprising a refrigerating device to pump refrigerated air into a set of shelves for receiving removable trays and a means for individually heating restricted sections in the trays. However, the tray cabinet of this patent is cooled by convection refrigeration rather than the more efficient conduction refrigeration of the present invention.
Another prior art device that provides for both heating and refrigeration features is disclosed in U.S. Pat. No. 4,346,756 to Dodd et al. This patent discloses an apparatus for selectively heating an individual food item in a refrigerated environment. Again, however, the apparatus of this patent is cooled by convection refrigeration rather than the conduction refrigeration of the present invention.
Other prior art devices that include heating and cooling features are disclosed in U.S. Pat. Nos. 3,205,033 to Stentz; 3,965,969 to Williamson; 3,982,584 to Spanoudis; and 4,103,736 to Colato et al. These prior art devices suffer some of the same deficiencies as de Filippis et al. and Dodd et al.
The above problems of prior art heating and holding cabinets and heating and cooling cabinets are addressed by the development of the present invention. The present invention is an improvement over the prior art and overcomes the problems associated with the prior art. The apparatus of the present invention provides consistent and superior heating and cooling transfer efficiencies because the apparatus utilizes principles of conduction heat/coolant transfer as opposed to using only the conventional convection heating/cooling technologies in common practice today.